CN105295434B - A method for jointly extracting red pigment and pectin from dragon fruit peel - Google Patents

Abstract

The invention discloses a method for combined extraction of haematochrome and pectin from pitaya peel. The method comprises the following specific steps: firstly chopping pitaya peel, blanching, drying, crushing, extracting by adding ethanol, filtering, and respectively collecting a filtrate and filter residue; carrying out extraction purification on the filtrate respectively by using a polyethylene glycol/ammonium sulfate aqueous two-phase system and trichloromethane so as to obtain a viscous pasty pitaya haematochrome; washing the filter residue with water to remove alcohol and carrying out heat insulation and acidolysis, processing by adding cation exchange resin and filtering, concentrating a filtrate, precipitating with ethanol, centrifuging, drying and crushing so as to obtain flaxen pectin powder. The method of the invention has advantages of simple equipment and low cost. In addition, high-purity haematochrome and high-ester pectin can be simultaneously extracted from pitaya peel. Thus, resource wasting caused by single extraction is avoided, and comprehensive utilization rate of pitaya can be remarkably raised.

Description

A method for jointly extracting red pigment and pectin from dragon fruit peel

technical field

The invention belongs to the technical field of comprehensive utilization and deep processing of agricultural and sideline products, and in particular relates to a method for jointly extracting red pigment and pectin from pitaya peel.

Background technique

Dragon fruit, also known as fairy honey fruit, red dragon fruit, etc., is a tropical fruit with high nutritional value. It has various health functions such as helping digestion, lowering blood pressure, lowering blood sugar, and anti-oxidation, and is deeply loved by consumers. In 2013, the planting area of dragon fruit in my country reached more than 100,000 mu, and there is still a trend of continuous expansion.

The skin of dragon fruit accounts for about a quarter of the fruit's weight, and it is rich in natural chemical components such as red pigment and pectin. However, in the process of food processing and daily consumption, dragon fruit peels are often discarded as waste, resulting in a huge waste of resources. The red pigment in the pitaya peel is mainly betaine and its glycosides, which have good physiological functions such as anti-oxidation, scavenging free radicals, improving immunity and anti-cancer, and can be used as natural food coloring or food with health care effects Additive; and pectin is the main component of soluble dietary fiber in the seven major nutrients of the human body, and it also has good gelling and emulsifying effects, and is widely used in the food, medicine and cosmetics industries.

Existing some utilize pitaya peel as raw material to extract the technological research of red pigment and pectin. Disclosed as patent CN 1631987A is a kind of method that extracts water-soluble red pigment from pitaya pulp, pericarp; Patent CN103497534A discloses a kind of utilizing supercritical CO _The method that fluid extracts pitaya peel pigment; Patent CN104212196A discloses a kind of pitaya Preparation method of red pigment in pericarp; Yuan Yafang et al. (“Isolation, purification and HPLC-MS analysis of red flesh dragon fruit pericarp pigment”, Journal of Fujian Agriculture and Forestry University (Natural Science Edition), 2013,42(6):589-592) Reported the separation and purification of pitaya peel pigment; Wang Biaoshi et al. ("Extraction of pitaya peel pigment and research on its antioxidant activity", Food Industry Science and Technology, 2013(43)5:234-238) reported The extraction of pitaya peel pigment and its antioxidant activity research; Wang Xue et al. Extraction of pectin and research on its structure; Optimization of pectin extraction process conditions. These patents and documents are all limited to the separation and extraction of a single component in the pitaya peel, and the raw materials cannot be fully utilized, and in the extraction process of these single components, some only obtain the crude product of red pigment and pectin. Among these crude products Contains a large amount of impurities such as sugars, and its quality cannot meet the industrial requirements; some processes use supercritical _CO2 fluid or high-performance liquid chromatography to separate and purify the red pigment. Although the purity meets the requirements, there are expensive equipment and high production costs. Insufficient; there are also macroporous adsorption resins for adsorption separation and purification. Although a large amount of impurities can be separated and removed, the adsorption and elution cycle of the resin is long, which increases the complexity of the operation.

Contents of the invention

The purpose of the present invention is to address the deficiencies in the prior art and provide a method for jointly extracting red pigment and pectin from pitaya peel. Comprehensive utilization of fruit peel resources.

To achieve the above object, the present invention adopts the following technical solutions:

A method for jointly extracting red pigment and pectin from pitaya peel, specifically comprising the following steps:

1) Mince the fresh dragon fruit peel, boil it in boiling water for 5-8 minutes to inactivate the pectinase, rinse it with clean water, dry it, and crush it;

2) Add the powder obtained in step 1) to ethanol with a mass concentration of 5-10 times its volume and 70%, extract at room temperature for 1-2 hours, filter, and collect the filtrate and filter residue respectively;

3) Concentrate the filtrate obtained in step 2) to dryness in vacuum at 50-55°C, and then extract and purify it with a polyethylene glycol/ammonium sulfate two-phase system; the dark red solution in the upper layer is polyethylene glycol containing red pigment solution, the lower layer of light red solution is ammonium sulfate solution containing impurities such as sugar;

4) Take step poly 3) the upper layer solution, add an equal volume of chloroform to extract, the red pigment enters the upper aqueous phase solution, polyethylene glycol enters the lower organic phase solution, and separates the dragon fruit red pigment and polyethylene glycol , collecting the upper layer aqueous phase solution;

5) Concentrate the aqueous phase solution obtained in step 4) in vacuum at 50-55°C to obtain sticky pitaya red pigment;

6) Rinse the filter residue obtained in step 2) with tap water to remove residual ethanol, then add deionized water 5 to 10 times the volume of the filter residue and oxalic acid with 1 to 3% of the weight of the filter residue, and adjust the pH of the solution to 3.0 to 3.6 with sodium hydroxide , then heated to 60~80°C, stirred slowly for 60min, filtered, and collected the filtrate;

7) Add the filtrate obtained in step 6) to the ion exchange resin, stir slowly at room temperature for 30~60min, filter, and collect the filtrate;

8) Vacuum concentrate the filtrate obtained in step 7) to 1/4~1/5 of the original volume, then add 1-2 times the volume of absolute ethanol, centrifuge, precipitate, dry, and pulverize to obtain light yellow Pectin powder.

Step 3) Extraction and purification of the polyethylene glycol/ammonium sulfate two-phase system is to add polyethylene glycol solution and ammonium sulfate solution to the filtrate, and after magnetic stirring for 20~30min, adjust the pH value of the solution to 5.0~ 5.5, let it stand at room temperature for 6~12 hours to make it layered;

The mass concentration of polyethylene glycol in the polyethylene glycol/ammonium sulfate two-phase system is 15 ~ 25%, and the mass concentration of ammonium sulfate is 10 ~ 15%; the molecular weight of polyethylene glycol used can be 2000, 4000 and 6000, preferably 6000.

The ion exchange resin described in step 7) is a strongly acidic cation exchange resin, and its dosage is 1-2% of the weight of the filter residue.

The ethanol used in step 2) and step 8) can be recycled after recovery.

Compared with the prior art, the present invention has the following significant advantages:

(1) The present invention has realized the combined extraction of two kinds of substances of pitaya peel red pigment and pectin, and the yield and purity are equivalent to the existing single extraction of a kind of material, but avoiding the waste of resources brought by single extraction, greatly The comprehensive utilization rate of Huoguolong has been improved.

(2) When extracting and purifying the red pigment of pitaya pericarp, the present invention first utilizes ethanol solution of lower concentration to extract, obtains the crude extract of red pigment, and then utilizes polyethylene glycol/ammonium sulfate two-phase system The red pigment in the crude extract is separated from impurities such as sugars. Since the polyethylene glycol/ammonium sulfate two-phase extraction technology can be carried out under mild conditions, the stability of the red pigment is guaranteed to the greatest extent, and its separation efficiency is high, the time is short, no large and complex equipment is required, and the operation is simple.

(3) Since the pitaya peel is rich in Ca ²⁺ and Mg ²⁺ ions, which have a blocking effect on pectin and will affect the transformation of protopectin into water-soluble pectin, the extraction rate of pectin by conventional acid extraction is low , The resulting pectin is of poor quality. The present invention uses oxalic acid instead of inorganic ^acids (hydrochloric acid, sulfuric acid, phosphoric acid, etc.) , Mg ²⁺ chelated water-insoluble pectin is extracted, and ion exchange resin is added to the pectin solution to absorb residual cations, which can improve the extraction rate and quality of pectin.

Description of drawings

Fig. 1 is the ultraviolet-visible spectrogram of the prepared pitaya peel red pigment solution of the present invention.

Fig. 2 is the ultraviolet-visible light spectrogram of the pitaya peel red pigment solution after single extraction and purification.

detailed description

In order to make the content of the present invention easier to understand, the technical solutions of the present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

Red pigment and pectin are jointly extracted in the pitaya peel

A method for jointly extracting red pigment and pectin from pitaya peel, specifically comprising the following steps:

1) Cut 400g of fresh dragon fruit peel with green scales removed into small pieces of 3-4mm in size, cook in boiling water for 5 minutes to inactivate pectinase, rinse with water for several times, press dry, and bake in an oven at 60°C for 12 hours. Then cool to room temperature, and pulverize into powder with a cooking machine; add ethanol with 5 times its volume and 70% mass concentration to the obtained powder, extract at room temperature for 2 hours, filter, and collect the filtrate and filter residue respectively;

2) Concentrate the filtrate obtained in step 1) to dryness in vacuum at 50°C, then add PEG6000 and ammonium sulfate solution, so that the mass concentration of polyethylene glycol in the obtained polyethylene glycol/ammonium sulfate two-phase system is 15% , the mass concentration of ammonium sulfate was 10%, and after magnetic stirring for 30min, the pH value of the solution was adjusted to 5.0, and left to stand at room temperature for 6h to make it layered. The dark red solution on the upper floor was a polyethylene glycol solution containing red pigment. The light red solution in the lower layer is an ammonium sulfate solution containing impurities such as sugars; take the upper layer solution of step poly, add an equal volume of chloroform and mix evenly, and centrifuge at 3000rpm for 10 minutes to make the red pigment enter the upper layer of the aqueous phase solution, polyethylene glycol Enter the organic phase solution of the lower layer, collect the upper layer aqueous phase solution; vacuum concentrate the aqueous phase solution obtained by step polymerization at 50°C to obtain 5.68g of water-soluble natural red pigment of pitaya in the form of viscous paste, with a yield of 1.42%;

3) Rinse the filter residue obtained in Step 1) with tap water to remove residual ethanol, then add deionized water 5 times the volume of the filter residue and oxalic acid with 3% weight of the filter residue, adjust the pH of the solution to 3.0 with sodium hydroxide, and then heat to 60°C , slowly stirred for 60min, filtered after 3000rpm centrifugation for 10min, and collected the filtrate; the filtrate obtained by step polymerization was added to 721 type strong acid cation exchange resin with 1% of the filter residue weight, slowly stirred for 60min at room temperature, filtered, and the filtrate was collected; the resulting filtrate was concentrated in vacuo to 1/4 of the original volume, then add 2 times the volume of absolute ethanol, place at room temperature for 2 hours, then centrifuge at 6000rpm for 10 minutes to obtain pectin precipitate, then dry the pectin precipitate in a vacuum dryer at 65°C, take it out and grind it finely to obtain The light yellow pectin powder is 1.93g. After conversion, the yield is 4.82g/kg (fresh weight). The degree of esterification of the obtained pectin is 64.6 as determined by FCC titration, which is high-ester pectin.

Take 1.0 g of the obtained dragon fruit red pigment, dissolve it in 100 mL of pure water, and scan its absorbance in the wavelength range of 400–660 nm, and the results are shown in Figure 1. The obtained pitaya red pigment has an obvious absorption peak in the visible light region, and its maximum absorption wavelength is 538nm, indicating that its main component is a betaine pigment. The absorbance value of the red pigment solution measured at 538nm is 0.830, and the color value of the pitaya red pigment is converted according to the color value calculation formula 538nm = 83.0.

The single extraction of red pigment in the pitaya peel of comparative example 1

1) Cut 400g of fresh dragon fruit peel with green scales removed into small pieces of 3-4mm in size, cook in boiling water for 5 minutes to inactivate pectinase, rinse with water for several times, press dry, and bake in an oven at 60°C for 12 hours. Then cool to room temperature, and pulverize into powder with a cooking machine; add ethanol with 5 times its volume and 70% mass concentration to the obtained powder, extract at room temperature for 2 hours, filter, and collect the filtrate;

2) Adsorb the obtained filtrate through D101 macroporous resin to obtain a macroporous resin adsorbed with dragon fruit red pigment, then elute the macroporous resin, collect the eluate, and use a rotary evaporator at a temperature of 50-55°C Concentrate under vacuum to obtain 6.42g of the water-soluble natural red pigment of pitaya of viscous paste, and the yield of red pigment is 1.60%.

Take 1.0 g of pitaya red pigment, dissolve it in 100 mL of pure water, and scan its absorbance in the wavelength range of 400-660 nm, the results are shown in Figure 2. The obtained pitaya red pigment has two obvious absorption peaks at 480nm and 538nm in the visible region, and these two wavelengths are respectively the maximum absorption wavelengths of betaflavin and betaflavin, indicating that after the crude extract of pitaya red pigment is purified by macroporous resin, There is still some betaflavin present. The absorbance value of the red pigment solution measured at 538nm is 0.698, and the color value of the pitaya red pigment is converted according to the color value calculation formula 538nm = 69.8.

The single extraction of pectin in the pitaya peel of comparative example 2

1) Cut 400g of fresh dragon fruit peel with green scales removed into small pieces of 3-4mm in size, cook in boiling water for 5 minutes to inactivate pectinase, rinse with water for several times, press dry, and bake in an oven at 60°C for 12 hours. Then cool to room temperature, crush into powder with a cooking machine; add 5 times the volume of deionized water to the obtained powder, adjust the pH to 1.5~1.6 with hydrochloric acid, stir and acidify at 80°C for 60 minutes, centrifuge at 3000rpm for 10 minutes, filter, and collect the filtrate The resulting filtrate was concentrated by rotary evaporation to 1/4 of the original volume, then added 2 times the volume of absolute ethanol, left at room temperature for 2 hours and then centrifuged at 6000rpm for 10 minutes to obtain pectin precipitates; dried the obtained pectin precipitates in a vacuum dryer at 65°C Dry it, take it out and grind it finely to get 1.58g of pectin powder. After conversion, the yield is 3.96g/kg (fresh weight). The degree of esterification of the obtained pectin is 31.4 as determined by FCC titration, which belongs to low-ester pectin. .

Through the comparison of Examples and Comparative Example 1, it can be seen that the red pigment yield of the joint extraction process is 1.42%, which is slightly lower than the single extraction red pigment extraction rate (1.60%), but its color value is significantly higher than that of the single extracted red pigment. The pigment shows that the red pigment obtained by the joint extraction of the present invention has high purity and good quality.

By the comparison of Examples and Comparative Example 2, it can be seen that the pectin extraction rate and pectin ester degree of the joint extraction process are significantly higher than that of the single extraction method, indicating that oxalic acid is used to replace hydrochloric acid to carry out acidolysis, combined with ion exchange method, can greatly improve Extraction yield and quality of pectin.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims (1)

1. a method for jointly extracting red pigment and pectin from dragon fruit peel, is characterized in that: comprise the following steps: 1) Chopped fresh dragon fruit peel, boiled in boiling water for 5-8 minutes, rinsed with water, dried and crushed; 2) Add the powder obtained in step 1) to ethanol with a mass concentration of 5 to 10 times its volume and a mass concentration of 70%, extract at room temperature for 1 to 2 hours, filter, and collect the filtrate and filter residue respectively; 3) Concentrate the filtrate obtained in step 2) to dryness in vacuum at 50-55°C, and then extract and purify it with polyethylene glycol/ammonium sulfate two-phase system; 4) Take the upper layer solution in step 3), add an equal volume of chloroform for extraction, and collect the upper layer aqueous phase solution; 5) Concentrate the aqueous phase solution obtained in step 4) in a vacuum at 50-55°C to obtain a viscous paste-like dragon fruit red pigment; 6) Rinse the filter residue obtained in step 2) with tap water, then add deionized water 5 to 10 times the volume of the filter residue and oxalic acid 1 to 3% of the weight of the filter residue, adjust the pH of the solution to 3.0 to 3.6 with sodium hydroxide, and then heat to 60 ~80°C, stir slowly for 60 minutes, filter, and collect the filtrate; 7) Add the filtrate obtained in step 6) to the ion exchange resin, stir slowly at room temperature for 30-60 minutes, filter, and collect the filtrate; 8) Vacuum concentrate the filtrate obtained in step 7) to 1/4~1/5 of the original volume, then add 1-2 times the volume of absolute ethanol, centrifuge, precipitate, dry, and crush to obtain light yellow fruit rubber powder; Step 3) Extraction and purification of the polyethylene glycol/ammonium sulfate two-phase system in the middle is to add polyethylene glycol solution and ammonium sulfate solution to the filtrate, and after magnetic stirring for 20~30min, adjust the pH value of the solution to 5.0~5.5 , stand at room temperature for 6~12h to make it layered; The mass concentration of polyethylene glycol in the polyethylene glycol/ammonium sulfate two-phase system is 15～25%, and the mass concentration of ammonium sulfate is 10～15%; The ion exchange resin described in step 7) is a strongly acidic cation exchange resin, and its dosage is 1-2% of the weight of the filter residue.